The grandly titled Special Rapporteur On The Rights To Freedom Of Peaceful Assembly And Of Association launched his attack on Britain during a three-day visit to London last week.

He met contentious figures including WikiLeaks founder Julian Assange, a radical students' leader accused of anti-Semitism, and members of a prisoners' rights group who called Jihadi John a 'beautiful young man'.

Last night former Defence Secretary Liam Fox hit back at Mr Kiai saying: 'With the level of oppression, abuse of human rights and terrorism around the world, I would think the United Nations would have better things to do with its resources and manpower than investigating one of the most peaceful, liberal and free countries.

'We don't make contributions to the UN to have them stick their noses into our country – we give them to improve the lot of people who don't know what freedom and security are.'

Mr Kiai is a Harvard-educated lawyer from Kenya which, its critics say, has far worse problems with human rights and terrorism than Britain does.

The capital Nairobi is home to the world's biggest slum, the Kenyan president has been accused of crimes against humanity, and Islamist group Al-Shabaab killed hundreds of people in massacres at a shopping mall and Garissa University.

In his role as Special Rapporteur, Mr Kiai was invited by the Government to observe freedom of association in Britain in 2013, and returned last week for an update. On the first day of his visit he met charities and members of 'civil society'.

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Mr Kiai was also photographed with his arm around Malia Bouattia (standing on Mr Kiai's right), the newly elected president of the National Union of Students.

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Mr Kiai also went to the Ecuadorian Embassy in Knightsbridge where Julian Assange has been granted asylum and has lived for almost four years since Britain's top court agreed to his extradition to Sweden for questioning over rape and sexual assault claims by two women

He was pictured shaking hands with Ibrahim Mohamoud, communications officer for CAGE, the prisoners' rights group that described IS executioner Mohammed Emwazi – known as Jihadi John – as a 'beautiful young man' who was 'extremely kind and gentle', and blamed his radicalisation on MI5.

Mr Kiai was also photographed with his arm around Malia Bouattia, the newly elected president of the National Union of Students.

She has caused a split in the union as she once claimed it was Islamophobic for the union to pass a motion condemning IS, and described Birmingham University, where she studied, as a 'Zionist outpost'.

Mr Kiai went on to meet MPs on the Joint Committee on Human Rights, travelled to the Home Office to see Policing Minister Mike Penning and Scotland Yard chiefs, and even took a lift in a patrol car to one of his appointments in Whitehall.

He also went to the Ecuadorian Embassy in Knightsbridge where Julian Assange has been granted asylum and has lived for almost four years since Britain's top court agreed to his extradition to Sweden for questioning over rape and sexual assault claims by two women. Mr Kiai was pictured smiling with Mr Assange.

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Mr Kiai went on to meet MPs on the Joint Committee on Human Rights, travelled to the Home Office to see Policing Minister Mike Penning (pictured right) and Scotland Yard chiefs

Mr Kiai delivered his damning verdict on the Government's anti-terror plans at a press conference after his meetings.

He said that the Prevent counter-radicalisation strategy actually risked 'promoting extremism' by alienating Muslims, and created a 'Big Brother' society that left families afraid to discuss terrorism in their own homes.

Mr Kiai is unpaid, but his visits and reports are paid for by the UN, to which the Foreign Office contributed £518 million last year.

A spokesman for the Office of the United Nations High Commissioner for Human Rights said: 'The funding for the Special Rapporteur On Freedom Of Peaceful Assembly And Association comes from the United Nations regular budget, which is approved by the General Assembly every two years.'